This expression is one that has given rise to a great deal of speculation about its origin, with various suggestions put forward.
We will start with the most gruesome proposals, which link “come hell or high water” to a form of medieval torture. There are essentially two main contenders here. The first would have us believe that “hell” was a burning hot poker inserted into the throat, with the “high water” being the drink subsequently given to the prisoner to “put the fire out”. The second torture has the prisoner forced to immerse the hand and arm in boiling water – “low water” up to the wrist and “high water” up to the elbow.
Whilst these are of course most unpleasant things to happen to anyone, it does not seem to me to be likely that they are the origin of our expression, meaning “whatever happens, in spite of any obstacle”. The expression separates the two parts: hell or high water, whereas here they are put together, and frankly, there seems to be very little evidence linking them to the expression in any case.
Let’s take a look at the second proposal. This derives the expression from the Bible, and again, there are two main contenders. I expect it comes as no surprise that many see the “high water” as a reference to the flood in Genesis, sent by God as a punishment to mankind, with Noah and his family the only survivors. In Gen 6:17, some English translations read “I shall bring high waters on the earth”, although others translate this as “floodwater”.
I also rather expect that the other biblical reference to “high water” is not so well known. This is in Isaiah 43:2.
“When you pass through deep (high) waters, I will be with you.”
My first thought on seeing this is that, despite obvious similarities, again it is not in keeping with our expression. This is because the implication of the verse is that the high waters here are not an obstacle, not a problem, because God is there.
The biblical proposals for the origin of “come hell or high water” generally see the “hell” part as a literal reference to the second coming of Christ, when hell will come to Earth.
Now we come to our last theory, which suggests that the phrase comes from the cattle ranches of the American mid-West. In the nineteenth century, cowboys drove their herds through rivers, whether the water was high or not, and of course a swollen river could present quite a challenge. A Washington Post article from November 1905 about cattle herders reads “…between the alien land law, drought and rustlers, the “hell and high water of the cattlemen,…”, linking the expression directly to this theory.
Not only that, but there is also an expression along the same lines used in the southern United States: “Lord willing and the creek don’t rise”. This seems to refer to a creek, which is a small stream, flooding, thereby giving us the same idea as the “high water”.
In Modern Greek, a popular expression in this context is βρέξει χιονίσει, (vrexei chionisei) which means “it rains, it snows”, which is similar to the other popular English phrase “come rain or shine”.
Across the Adriatic in Italy, people say cascasse il mondo, which translates as “should the world fall”, an image of disaster perhaps akin to the idea of hell coming. Perhaps in a similar vein, the Polish expression is choćby się waliło i paliło, which means “even if it tumbles down and burns”. Another nice apocalyptic image!
In keeping with this theme of doom, Slovene has an interesting idiom: pa tudi, če vse hudič vzame, or “even if the devil takes everything”.
In this case, I am rather partial to the Turkish saying, which seems a little gruesome! It is; iki elim kanda olsa, meaning “if both my hands are in blood”. Perhaps not as disastrous as the English and Italian, but still very unpleasant!